<!DOCTYPE html>
<html>
<head>
  <style>
    body { margin: 0 }
    div.ref {
      border: 1px solid black;
      box-sizing: border-box;
      background: green;
      height: 50px;
      width: 100px;
    }
  </style>
</head>
<body>
  <div class="ref"></div>
</body>
</html>
